Described herein are medical devices for placing an implant such as an embolic device at a predetermined site within a vessel or lumen of a human (or animal) body. For example, described herein are catheter-based deployment apparatuses for delivering an embolic device such as a coil. These apparatuses are particularly suited to transport an embolic device, such as an embolic coil, through the vasculature of the human brain to a selected site within the vessel or within an aneurysm, and may address many of the problems identified with prior art systems, as will be briefly described below.
For many years, flexible catheters have been used to place various devices within the vessels of the human body. Such devices may include dilation balloons, radiopaque fluids, liquid medications, and various types of occlusion devices such as balloons and embolic coils. Examples of such catheter-based devices are disclosed in U.S. Pat. No. 5,108,407, entitled, “Method and Apparatus for Placement of an Embolic Coil” and U.S. Pat. No. 5,122,136, entitled, “Endovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” These patents disclose catheter-based devices for delivering embolic coils to preselected positions within vessels of the human body in order to treat aneurysms, or alternatively, to occlude blood vessels at a particular location.
Coils which are placed in vessels may take the form of helically wound coils, or alternatively, may take the form of randomly wound coils, coils wound within coils or other such coil configurations. FIGS. 1 and 2 illustrate examples of coils that may be used; such coils may have complex and helical shapes to accommodate a broad range of patient anatomy. For example, coils may have a complex frame of about 2 mm×3 cm to 15 mm×50 cm (e.g., 1 mm×2 cm to 5 mm×10 cm). Coils may be made ultra soft, soft or standard flexibility and, may include a Polymer or metallic Stretch Resistant (SR) Member. Other examples of various coil configurations are disclosed in U.S. Pat. No. 5,334,210, entitled, “Vascular Occlusion Assembly” and U.S. Pat. No. 5,382,259 entitled, “Vasoocclusion Coil with Attached Tubular Woven or Braided Fibrous Covering.” Embolic coils are often formed of a radiopaque metallic material, such as platinum, gold, tungsten, or alloys of these metals. Several coils may be placed at a given location to occlude the flow of blood through the vessel, or aneurysm, by promoting thrombus formation at the particular site.
In the past, embolic coils have been placed within the distal end of a catheter. When the distal end of the catheter is properly positioned, the coil may then be pushed out of the end of the catheter with a pusher member to release the coil at the desired location. This procedure for placement of an embolic coil may be conducted under fluoroscopic visualization such that the movement of the coil through the vasculature of the body may be monitored and the coil placed at the desired location.
In some procedures, glue or solder may be used to attach a coil to a guidewire, which in turn, is placed within a flexible catheter for positioning the coil within the vessel at a preselected position. Once the coil is in the desired position, the coil is held in position by the catheter and the guidewire is pulled proximally to thereby cause the coil to become detached from the guidewire and released from the catheter. Such a coil positioning system is disclosed in U.S. Pat. No. 5,263,964 entitled, “Coaxial Traction Detachment Apparatus and Method.”
Still another coil positioning procedure is that of having a catheter with a socket at the distal end of the catheter for retaining a ball which is, in turn, bonded to the proximal end of the coil. The ball, which is generally larger in diameter than the outside diameter of the coil, is placed in the socket within the lumen at the distal end of the catheter and the catheter is then moved into a vessel in order to place the coil at a desired position. Once the position is reached, a pusher wire with a piston at the end thereof is pushed distally from the proximal end of the catheter to push the ball out of the socket in order to release the coil at the desired position. Such a system is disclosed in U.S. Pat. No. 5,350,397, entitled, “Axially Detachable Embolic Coil Assembly.” A similar prior art apparatus is shown in FIG. 3, which is described in U.S. Pat. No. 5,895,391, titled “Ball Lock Joint and Introducer for Vaso-Occlusive Member”. In this example, an interference wire is used to drive the large ball attached to the end of the coil into a retaining seat on the device. Once the distal end of a delivery catheter is positioned at a target site, the vaso-occlusive device 222 is engaged within a holding member 226 and is inserted and forwarded to the chosen target site in the body. The interference wire 228 is in such a position during this introductory step so that the whole assembly may be forwarded through the catheter as an assembly. Once positioned, the interference wire is removed and the catheter, holding member, and interference wire are each withdrawn from the body.
Another procedure for placing an embolic coil within a vessel is that of using a heat releasable adhesive bond for retaining the coil at the distal end of the catheter. One such system uses laser energy transmitted through a fiber optic cable to apply heat to the adhesive bond in order to release the coil from the end of the catheter. Such a procedure is disclosed in U.S. Pat. No. 5,108,407, entitled “Method and Apparatus for Placement of an Embolic Coil.”
Yet another coil deployment system incorporates a catheter having a lumen throughout the length of the catheter and a distal tip for retaining the coil for positioning the coil at a preselected site. The distal tip of the catheter is formed of a material which exhibits the characteristic that when the lumen of the catheter is pressurized the distal tip expands radially to release the coil at the preselected site. Such a deployment system is disclosed in U.S. Pat. No. 6,113,622, entitled, “Embolic Coil Hydraulic Deployment System.”
Still another coil deployment system incorporates an interlocking mechanism on the coil. The interlocking end on the embolic coil couples with a similar interlocking mechanism on a pusher assembly. A control wire which extends through the locking mechanism secures the coil to the pusher assembly. The pusher assembly and embolic coil are initially disposed within the lumen of a catheter. When the embolic coil is pushed out of the end of the catheter for placement, the control wire is retracted and the coil disengages from the pusher assembly. Such a deployment system is disclosed in U.S. Pat. No. 5,925,059, entitled, “Detachable Embolic Coil Assembly.”
Yet another coil deployment system incorporates an embolic device detachably mounted on the distal portion of a pusher member and held in place with a connector thread or fiber. The fiber passes through a cutter member that may be activated to cut the connector fiber. Once the connector fiber is cut, the embolic device is released. Such a deployment system is disclosed in Published U.S. Patent Application Publication No. 2002/0165569, entitled, “Intravascular Device Deployment Mechanism Incorporating Mechanical Detachment.”
Another coil deployment system incorporates an embolic device with a stretch resistant member therethrough. The distal end of the stretch resistant member attaches to the embolic coil and the proximal end of the stretch resistant member is detachably mounted on the pusher member through various means such as adhesive, or by a connector fiber adhered to or tied to the pusher member, and is detachable by the application of heat. Such a deployment system is disclosed in U.S. Patent Application Publication No. 2004/0034363, entitled, “Stretch Resistant Therapeutic Device.”
Still another coil deployment system incorporates a pusher wire with a stiff wavy-shaped end segment which is coupled to the embolic coil and is placed in the lumen of the catheter. The coil is advanced through the catheter until it reaches a predetermined site in the vessel at which time the pusher wire is retracted and the embolic coil is released. Such a system is disclosed in U.S. Pat. No. 6,203,547, entitled, “Vaso-occlusion Apparatus Having A Manipulable Mechanical Detachment Joint And A Method For Using The Apparatus.”
The various deployment systems described above may all be used to deliver one or more implants to a target site, but each of these systems may be improved. In particular, for non-mechanical systems (e.g., electrical, chemical or hydraulic release systems, the response time of actuating is delayed, which may lead to error and frustration on the part of the surgeon. Many of the mechanical delivery systems described herein also suffer from problems associated with the reliability and robustness of the apparatus and method of operation. Further, implants that are mechanically releasing implants from known systems may not be released with sufficient force, and may require direct visualization to confirm release. Described herein are methods and apparatuses that may address these deficiencies.